1. Field of the Invention
The present invention relates to an image forming apparatus including a developing device, including a developer bearing member for bearing a developer on its surface and conveying the developer, using an electrophotographic method for developing a latent image formed on an image bearing member.
2. Description of the Related Art
Conventionally, a developing device for bearing a developer on a surface of a developer bearing member, conveying and supplying the developer to the vicinity of a surface of an image bearing member having an electrostatic latent image borne thereon, and developing and visualizing the electrostatic latent image while applying an alternating (alternating current) electric field between the image bearing member and the developer bearing member has been well known.
The developing device reaches its lifetime end due to deterioration of the developer or deterioration of the developer bearing member by repeatedly performing image formation. When the developer deteriorates, defects such as fogging on a blank portion and toner scattering occur. The developer bearing member is driven to rotate as the image formation is performed, so that defects such as thin image density, image unevenness, and fogging on the blank portion occur due to surface abrasion or the like.
Japanese Patent Application Laid-Open No. 9-190142 discusses a technique for integrating a driving time of a developer bearing member and determining a lifetime end of a developing device based on an integrated value of the driving time.
Surface abrasion occurs due to physical pressure at the time of driving. Therefore, a certain degree of prediction can be made by integrating the driving time, as discussed in Japanese Patent Application Laid-Open No. 9-190142. However, deterioration of performance occurring when the developer bearing member reaches its lifetime end includes deterioration by surface abrasion and deterioration by surface adhesion of the developer. The developing device may reach its lifetime end by the developer adhering to the surface of the developer bearing member prior to the surface abrasion. In such a case, the lifetime end cannot be correctly detected, resulting in image defects.